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International audience; Casuarina equisetifolia Forst., a member of the Casuarinaceae family, is widely planted in coastal areas due to its ability to function as potential barrier against wind and waves. Significant variation has been reported in the ability of C. equisetifolia to grow under salinity stress. In the present study, 82 clones of C. equisetifolia were assessed for their response to 50 mM incremental NaCl concentrations ranging from 50 mM to 550 mM in Hoagland's solution and clones with contrasted salt tolerance were identified. Several earlier reports attribute salt sensitivity in Casuarina species to the toxic effect of sodium. Intraclonal variation in the levels of sodium accumulation was therefore analysed. However, sodium content in the shoots and roots, showed little correlation (0.351 and -0.171) with salt tolerance in C. equisetifolia. Similarly, sodium to potassium ratio in the shoots and roots of NaCl treated and untreated clones also did not show correlation with mortality although certain tolerant clones exhibited selectivity of potassium over sodium under salt stress. Analysis of the shoot to root ratio of sodium however, showed better correlation (0.448) with salt tolerance, suggesting that restricted translocation of sodium to shoots and its relative retention in roots might play a crucial role in the salt tolerant clones of C. equisetifolia, and that shoot to root ratio of sodium could be a better parameter for salt tolerance in C. equisetifolia clones. The higher salt tolerance observed in certain clones despite higher sodium accumulation or shoot to root ratio of sodium suggests the presence of different multiple adaptive mechanisms that may be operating in different clones to help protect the cells from the toxic effects of sodium. The tolerant clone, TNIPT 4, which accumulated high concentrations of Na+, had low shoot to root ratio of Na+, and also a higher constitutive as well as NaCl induced accumulation of the compatible osmolyte, proline. The study thus emphasizes the need for characterising the genetic components involved in sodium transport, proline metabolism and other mechanisms contributing to salinity tolerance. The identified clones with contrasted stress tolerance mechanisms would thus be a valuable resource for transcriptomic, proteomic and metabolomic exploration in addition to their utility for field evaluation in flooded and coastal saline tracts.

One of the major classes of antioxidant enzymes, which protect the cellular and subcellular components against harmful reactive oxygen species (ROS), is superoxide dismutase (SOD). SODs play pivotal role in scavenging highly reactive free oxygen radicals and protecting cells from toxic effects. In Oryza sativa three types of SODs are available based on their metal content viz. Cu-Zn SOD, Mn SOD and Fe SOD. In the present study attempts were made to critically assess the structure and phylogenetic relationship among Oryza sativa SODs. The sequence similarity search using local BLAST shows that Mn SODs and Fe SODs have greater degree of similarity compared with that of Cu-Zn SODs. The multiple alignment reveals that seven amino acids were found to be totally conserved. The secondary structure shows that Mn SODs and Fe SODs have similar helixes, sheets, turns and coils compared with that of Cu-Zn SODs. The comparative analysis also displayed greater resemblance in primary, secondary and tertiary structures of Fe SODs and Mn SODs. Comparison between the structure and sequence analysis reveals that Mn SOD and Fe SOD are found to be closely related whereas Cu-Zn SOD evolves independently.

Background Eucalyptus is grown in around 3.9 Mha in India.Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) has emerged as a serious pest in Eucalyptus causing considerable loss of quality planting materials besides loss in productivity and quality of timber. Current strategies for its control include selected deployment of Eucalyptus clones tolerant to the pest resulting in several productive Eucalyptus genetic resources, not being considered for plantation programmes, as in the case of the widely planted Eucalyptus clone, ITC 10, and ITC 271. The securely ensconced grub within the gall for a period of around 4 months post oviposition makes it refractory to pesticide applications. This feature, however, makes plant- incorporated protectants, via RNAi approaches a potential strategy for engineering resistance [1-3]. However, application of RNAi technology requires determination of sequence information of insect-specific genes so that off-target effects in plants as well as human beings are avoided. Methods

Background The wide adaptability, fast growth rate, good form, excellent wood and fiber properties make Eucalyptus the most widely planted genus of plantation forest trees. With the availability of Eucalyptus genome sequence information, assignment of function to genes contributing to desired traits require functional validation via overexpression or silencing in the context of the plant environment. However, plant regeneration from transformed tissues has been the most time consuming and rate-limiting step for rapid gene function analysis in tree species. The composite plants with transgenic hairy roots derived via Agrobacterium rhizogenes mediated transformation are therefore increasingly being used in species with such limitations to study root development and root-biotic interactions [1]. In this paper we describe a protocol developed for generation of composite plants using A. rhizogenes mediated transformation of Eucalyptus camaldulensis.